Book Image

Mastering JavaScript Functional Programming - Second Edition

By : Federico Kereki
Book Image

Mastering JavaScript Functional Programming - Second Edition

By: Federico Kereki

Overview of this book

Functional programming is a paradigm for developing software with better performance. It helps you write concise and testable code. To help you take your programming skills to the next level, this comprehensive book will assist you in harnessing the capabilities of functional programming with JavaScript and writing highly maintainable and testable web and server apps using functional JavaScript. This second edition is updated and improved to cover features such as transducers, lenses, prisms and various other concepts to help you write efficient programs. By focusing on functional programming, you’ll not only start to write but also to test pure functions, and reduce side effects. The book also specifically allows you to discover techniques for simplifying code and applying recursion for loopless coding. Gradually, you’ll understand how to achieve immutability, implement design patterns, and work with data types for your application, before going on to learn functional reactive programming to handle complex events in your app. Finally, the book will take you through the design patterns that are relevant to functional programming. By the end of this book, you’ll have developed your JavaScript skills and have gained knowledge of the essential functional programming techniques to program effectively.
Table of Contents (17 chapters)
Technical Requirements

Chapter 12, Building Better Containers – Functional Data Types

12.1. Maybe tasks? The following code shows a simpler solution than the one we looked at in question 8.2:

const pending = Maybe.of(listOfTasks)
.map(filter(t => t.responsible === name))
.map(t => tasks)
.map(t => t[0])
.map(filter(t => !t.done))

Here, we apply one function after the other, secure in the knowledge that if any of these functions produces an empty result (or even if the original listOfTasks is null), the sequence of calls will go on. In the end, you will either get an array of task IDs or a null value.

12.2. Extending your trees: Calculating the tree's height is simple if you do this in a recursive fashion. The height of an empty tree is zero, while the height of a non-empty tree is one (for...